In order to produce hot strips, in general, slabs are heated to a predetermined temperature in heating furnaces, and the heated slabs are rolled into rough bars having a predetermined thickness in roughing stands. Subsequently, the rough bars are rolled into steel strips having a predetermined thickness in continuous finishing stands including a plurality of rolling stands. After the steel strips are cooled by cooling devices on run-out tables, the strips are coiled by down coilers.
In order to cool the upper sides of the steel strips, the cooling devices on the run-out tables for continuously cooling hot-rolled steel strips pour laminar flows of cooling water from laminar flow nozzles of the round type onto roller tables for conveying steel strips linearly over the width of the roller tables. On the other hand, in order to cool the lower sides of the steel strips, spray nozzles are disposed between two adjacent roller tables in general so as to eject cooling water.
However, in such known cooling devices, the flows of the cooling water from the laminar flow nozzles used for cooling the upper sides of the steel strips are free-fall flows. This can cause problems such as variation in cooling capacity in accordance with the existence of water remaining on the upper surfaces of the steel strips since it is difficult for the cooling water to reach the steel strips when water films of the remaining water exist on the upper surfaces of the steel strips and unstable cooling capacity in response to changes in cooling areas (cooling zones) caused when the cooling water falling on the steel strips freely expands in all directions. As a result of the variation in the cooling capacity, the properties of the steel strips easily become uneven.
In order to achieve a stable cooling capacity by draining the cooling water (remaining water) on the upper surfaces of the steel strips, a method for discharging remaining water by ejecting fluid obliquely across upper surfaces of steel strips (for example, Patent Document 1) and a method for damming up remaining water using a restraining roller for restraining vertical movement of steel strips as a draining roller so as to stabilize cooling areas (for example, Patent Document 2) have been proposed.
Herein, Patent Document 3 is also described below since the document is cited in the section of “Best Modes for Carrying Out the Invention”.                Patent Document 1: Japanese Unexamined Patent Application Publication No. 9-141322        Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-166023        Patent Document 3: Japanese Unexamined Patent Application Publication No. 2002-239623        